New charge category model for SROC supplementary bill run (#57)

https://eaflood.atlassian.net/browse/WATER-3861

Behind the scenes, the charge references are held in the billing_charge_categories table. It is a lookup table as the references are static. They are linked to a charge version via the charge_elements table.

app/models/billing-charge-category.model.js

@@ -0,0 +1,31 @@
+'use strict'
+
+/**
+ * Model for water.billing_charge_categories
+ * @module BillingChargeCategoryModel
+ */
+
+const { Model } = require('objection')
+
+const BaseModel = require('./base.model.js')
+
+class BillingChargeCategoryModel extends BaseModel {
+  static get tableName () {
+    return 'water.billing_charge_categories'
+  }
+
+  static get relationMappings () {
+    return {
+      chargeElement: {
+        relation: Model.HasManyRelation,
+        modelClass: 'charge-element.model',
+        join: {
+          from: 'water.billing_charge_categories.billing_charge_category_id',
+          to: 'water.charge_elements.billing_charge_category_id'
+        }
+      }
+    }
+  }
+}
+
+module.exports = BillingChargeCategoryModel

app/models/charge-element.model.js

@@ -23,6 +23,14 @@ class ChargeElementModel extends BaseModel {
           from: 'water.charge_elements.charge_version_id',
           to: 'water.charge_versions.charge_version_id'
         }
+      },
+      billingChargeCategory: {
+        relation: Model.BelongsToOneRelation,
+        modelClass: 'billing-charge-category.model',
+        join: {
+          from: 'water.charge_elements.billing_charge_category_id',
+          to: 'water.billing_charge_categories.billing_charge_category_id'
+        }
       }
     }
   }

db/migrations/20221216112650_create_billing_charge_categories.js

@@ -0,0 +1,43 @@
+'use strict'
+
+const tableName = 'billing_charge_categories'
+
+exports.up = async function (knex) {
+  await knex
+    .schema
+    .withSchema('water')
+    .createTable(tableName, table => {
+      // Primary Key
+      table.uuid('billing_charge_category_id').primary().defaultTo(knex.raw('gen_random_uuid()'))
+
+      // Data
+      table.string('reference')
+      table.integer('subsistence_charge')
+      table.string('description')
+      table.string('short_description')
+      table.boolean('is_tidal')
+      table.string('loss_factor')
+      table.string('model_tier')
+      table.boolean('is_restricted_source')
+      table.bigInteger('min_volume')
+      table.bigInteger('max_volume')
+
+      // Automatic timestamps
+      table.timestamps(false, true)
+    })
+
+  await knex.raw(`
+    CREATE TRIGGER update_timestamp
+    BEFORE UPDATE
+    ON water.${tableName}
+    FOR EACH ROW
+    EXECUTE PROCEDURE update_timestamp();
+  `)
+}
+
+exports.down = function (knex) {
+  return knex
+    .schema
+    .withSchema('water')
+    .dropTableIfExists(tableName)
+}

test/models/billing-charge-category.model.test.js

@@ -0,0 +1,30 @@
+'use strict'
+
+// Test framework dependencies
+const Lab = require('@hapi/lab')
+const Code = require('@hapi/code')
+
+const { describe, it } = exports.lab = Lab.script()
+const { expect } = Code
+
+// Thing under test
+const BillingChargeCategory = require('../../app/models/billing-charge-category.model.js')
+
+describe('Billing Charge Category model', () => {
+  it('can successfully run a query', async () => {
+    const query = await BillingChargeCategory.query()
+
+    expect(query).to.exist()
+  })
+
+  describe('Relationships', () => {
+    describe('when linking to charge element', () => {
+      it('can successfully run a query', async () => {
+        const query = await BillingChargeCategory.query()
+          .innerJoinRelated('chargeElement')
+
+        expect(query).to.exist()
+      })
+    })
+  })
+})

test/models/charge-element.model.test.js

@@ -26,5 +26,14 @@ describe('Charge Element model', () => {
         expect(query).to.exist()
       })
     })
+
+    describe('when linking to billing charge category', () => {
+      it('can successfully run a query', async () => {
+        const query = await ChargeElement.query()
+          .innerJoinRelated('billingChargeCategory')
+
+        expect(query).to.exist()
+      })
+    })
   })
 })

test/support/helpers/billing-charge-category.helper.js

@@ -0,0 +1,69 @@
+'use strict'
+
+/**
+ * @module BillingChargeCategoryHelper
+ */
+
+const { db } = require('../../../db/db.js')
+
+/**
+ * Add a new billing charge category
+ *
+ * If no `data` is provided, default values will be used. These are
+ *
+ * - `reference` - 4.4.5
+ * - `subsistence_charge` - 12000
+ * - `description` - Low loss non-tidal abstraction of restricted water up to and including 5,000 megalitres a year, where a Tier 1 model applies.
+ * - `short_description` - Low loss, non-tidal, restricted water, up to and including 5,000 ML/yr, Tier 1 model
+ * - `is_tidal` - false
+ * - `loss_factor` - low
+ * - `model_tier` - tier 1
+ * - `is_restricted_source` - true
+ * - `min_volume` - 0
+ * - `max_volume` - 5000
+ *
+ * @param {Object} [data] Any data you want to use instead of the defaults used here or in the database
+ *
+ * @returns {string} The ID of the newly created record
+ */
+async function add (data = {}) {
+  const insertData = defaults(data)
+
+  const result = await db.table('water.billing_charge_categories')
+    .insert(insertData)
+    .returning('billing_charge_category_id')
+
+  return result
+}
+
+/**
+ * Returns the defaults used when creating a new billing charge category
+ *
+ * It will override or append to them any data provided. Mainly used by the `add()` method, we make it available
+ * for use in tests to avoid having to duplicate values.
+ *
+ * @param {Object} [data] Any data you want to use instead of the defaults used here or in the database
+ */
+function defaults (data = {}) {
+  const defaults = {
+    reference: '4.4.5',
+    subsistence_charge: 12000,
+    description: 'Low loss non-tidal abstraction of restricted water up to and including 5,000 megalitres a year, where a Tier 1 model applies.',
+    short_description: 'Low loss, non-tidal, restricted water, up to and including 5,000 ML/yr, Tier 1 model',
+    is_tidal: false,
+    loss_factor: 'low',
+    model_tier: 'tier 1',
+    is_restricted_source: true,
+    min_volume: 0,
+    max_volume: 5000
+  }
+
+  return {
+    ...defaults,
+    ...data
+  }
+}
+
+module.exports = {
+  add
+}